Try this for starters.
Select Top (1000000) tsysOS.Image As icon,
tblAssets.AssetID,
tblAssets.AssetName,
tblAssets.Domain,
tblAssets.Username,
tblAssets.Userdomain,
tblAssets.IPAddress,
tblAssets.Description,
tblAssetCustom.Manufacturer,
tblAssetCustom.Model,
tblAssetCustom.Location,
tsysIPLocations.IPLocation,
tsysOS.OSname As OS,
tblAssets.SP,
tblAssets.Firstseen As [Created at],
tblAssets.Lastseen As [Last successful scan]
From tblAssets
Inner Join tblComputersystem On tblAssets.AssetID = tblComputersystem.AssetID
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysOS On tblAssets.OScode = tsysOS.OScode
Left Outer Join tsysIPLocations On tsysIPLocations.LocationID =
tblAssets.LocationID
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Where tblAssets.AssetID Not In (Select tblSoftware.AssetID
From tblSoftware Inner Join tblSoftwareUni On tblSoftwareUni.SoftID =
tblSoftware.softID Inner Join tsysantivirus On
tblSoftwareUni.softwareName Like tsysantivirus.Software) And
tblAssets.AssetID Not In (Select tblAntivirus.AssetID
From tblAntivirus) And tblComputersystem.Domainrole <= 1 And
tblAssetCustom.State = 1
Order By tblAssets.AssetName